A circuit breaker is used to protect an electric circuit from damage caused by a persistent overcurrent condition, short circuit, fault or other anomaly. During normal operation, mating contacts located within the circuit breaker are kept in a closed position to enable current flow through the circuit. When a fault condition is detected, the contacts are automatically opened, thus interrupting the circuit and disengaging the circuit from a power supply (i.e., the circuit breaker is tripped). The circuit breaker may also be manually tripped by moving a breaker trip bar. Movement of the trip bar releases a trip mechanism that holds the contacts in the closed position, thus opening the contacts.
A circuit breaker may be used in conjunction with a circuit breaker accessory such as a shunt trip device. A shunt trip device enables remote tripping of a circuit breaker. For example, a shunt trip device enables emergency personnel arriving at a building fire to remotely trip a circuit breaker from a control panel in order to enhance personnel safety and protect equipment.
A shunt trip device includes a device housing that is relatively small and has limited internal space. The device housing holds a solenoid having a moveable plunger, a lever for moving the trip bar and other components. When the solenoid is energized, the plunger pushes on the lever and the lever then moves the trip bar and trips the circuit breaker. Frequently, the force/torque and displacement requirements for moving the trip bar are greater than the available force from the solenoid and/or greater than the leverage provided by the lever. In order to provide additional force/torque to move the trip bar, a larger solenoid having additional capacity may be used. However, a larger solenoid draws relatively large amounts of current which is not desirable to customers and would occupy additional space in the device housing.
Alternatively, a larger lever may be used in order to increase a force multiplier effect provided by the lever. However, a larger lever requires a large space in the device housing. Further, the lever rotates about a pin formed in the device housing as part of a pin-pivot arrangement. Referring to FIG. 1, a lower portion of an conventional lever 5 having hole 7 for receiving a pin is shown. In a pin-pivot arrangement, an area 9 around the pin in the device housing must be sufficiently large so to accommodate both a hole for the pin and a material web needed around the hole to support the pin. This further takes up the limited available space in the device housing. Moreover, the pin-pivot arrangement is prone to assembly errors, thus increasing manufacturing costs.